The present invention relates to a device for distributing materials in bulk with a rotary chute having a variable angle of inclination.
Such devices are used, for example, in devices for charging shaft furnaces, particularly blast furnaces, in which a rotary chute with a variable angle of inclination provides for the distribution of the charge inside the shaft furnace. More particularly, they comprise a supporting cage in which a suspension rotor is mounted in such a way that it can be driven in rotation about a substantially vertical rotation axis. The chute is suspended from this rotor so that it can pivot about its suspension axis. A pivoting mechanism makes it possible to change the inclination of the chute during its rotation. The rotor is traversed axially by a feed channel so that the materials in bulk, which flow from a batch hopper in the charging device, are poured into the rotary chute, which distributes them inside the shaft furnace.
Such devices for distributing materials in bulk are, for example, described in the documents WO 95/21272, U.S. Pat. Nos. 5,022,806, 4,941,792, 4,368,813, 3,814,403 and 3,766,868. In these devices, the pivoting mechanism comprises a second rotor, which has a rotation axis substantially coaxial with the first rotor, from which the chute is suspended. This second rotor may be driven in rotation at a different speed from that of the first rotor, which makes it possible to produce a variable angular displacement between the two rotors. A mechanism connected between the second rotor and the chute then enables a variation in the angular displacement between the two rotors to be converted into a variation of the angle of inclination of the chute in its vertical pivoting plane.
A different type of device for the distribution of materials in bulk is known from the document FR 22230246. This device includes an outer casing in which a rotating barrel is supported. This rotating barrel supports an oscillating chute in journals. The journals carry cranks connected by linking rods to a first circular ring. The ladder is locked in rotation with the rotating barrel by fingers that can slide vertically in guides fixed to the rotating barrel and it is carried by a second circular ring on which it is centered and on which it rests and freely rotates through the intermediary of rollers. The second circular ring is supported at several points by linking rods connected to the connecting rods of jacks mounted on the outer casing. By substantially adjusting the vertical position of the second ring using jacks, it is possible to adjust the inclination of the chute.
In general, it is important to note that the torque which must be transmitted to the chute to make it pivot about its horizontal pivoting axis may become very high, particularly if the chute has a very massive construction (as is the case, for example, on blast furnaces), and/or if the pivoting is of large amplitude. It follows that large forces must be transmitted by the pivoting mechanism for the chute.
One of the problems underlying the present invention is that of proposing a device for distributing materials in bulk with a rotary chute having a variable angle of inclination, in which a relatively simple pivoting mechanism for the chute is used, which nevertheless has excellent qualities as regards the transmission of the large forces necessary for the pivoting of the chute.
This problem is solved by a device according to the present invention. Such a device comprises, in a way know per se, a suspension rotor mounted in a supporting cage so that it can rotate about a substantially vertical rotation axis. The chute is suspended from this rotor so that it can pivot about a substantially horizontal suspension axis. The suspension rotor is traversed axially by a feed channel for the chute. The device includes a very simple pivoting mechanism for changing the inclination of the chute suspended from the rotor. This mechanism consists of a first and second ring, which are both located around the rotor, so that their central axis is coaxial with the rotation axis of the rotor. A guidance device, locked in rotation with the rotor, is connected between the rotor and the first ring, so that the latter can slide axially along the rotor. At least one connecting element connects the first ring to the chute so as to convert a vertical sliding of the first ring into a pivoting of the chute about its pivoting axis. The first and second rings are connected through the intermediary of a bearing ring. An annular hydraulic jack, which is positioned around the suspension rotor so that its central axis is coaxial with the rotation axis of the latter, is connected to the second ring in order to produce a variation in its vertical position. Hence, by changing, using this annular hydraulic jack, the vertical position of the second non-rotatable ring, the first ring is made to slide vertically along the rotor using the guidance device and this produces a pivoting of the chute about its pivoting axis. It should be appreciated that the mechanism formed by the annular hydraulic jack, the two rings, the bearing ring and the guidance device forms an ingenious and reliable chain of transmission for large pivoting forces.
The chute preferably incorporates two lateral suspension arms and the rotor two lateral bearings in which the suspension arms are suspended so that the chute can pivot about a substantially horizontal axis. Connecting rods can then connect the first ring to each of the suspension arms of the chute so as to convert a vertical sliding of the first ring into a pivoting of the chute around its pivoting axis.
The guidance device connected between the first ring and the rotor preferably consists of several vertical rails mounted on the rotor and rollers mounted on the first ring and guided in the rails. Excellent guidance is obtained when a pair of vertically separated rollers is guided in each rail.
In an alternative embodiment, the means for control used to vary the vertical position of the second ring comprise a lever mechanism and a hydraulic jack which actuates this lever mechanism. This lever mechanism then preferably consists of an intermediate articulated lever provided with a supporting arm and an actuating arm. The supporting arm advantageously has the shape of a fork connected to the second ring at two diametrically opposite points, for example by means of connecting rods. The actuating arm is connected outside the supporting cage to the hydraulic jack so that the latter can be easily replaced and is no longer exposed to a hostile environment inside the supporting cage. If the device for distributing materials in bulk is used, for example, on a shaft furnace, the supporting cage is preferably a sealed structure. The lever then advantageously comprises a suspension pivot which carries the actuating arm and which leaves the supporting cage imperviously through a suspension bearing form, an integral part of the sealed structure.
It should be appreciated that a description is also given of simple and effective methods for protecting the components inside the supporting cage particularly against heat. Thus it is proposed, for example, to insert a non-rotatable tubular screen fitted with a cooling circuit between the feed channel and the suspension rotor. It is also proposed to provide the supporting cage at its lower end with a fixed annular screen, which is fitted with a cooling circuit and defines a circular central opening, while the suspension rotor is fitted at its lower end with a flange which is set with some clearance in this circular central opening. A gas injection pipe is in this case advantageously positioned along the circular central opening of the fixed annular screen so that a coolant gas can be injected into cavities opening into the lateral edge of the flange.